1. Field of the Invention
The present invention relates to a battery pack provided therein with a compact battery having large output which drives an ultra-compact electric motor for starting a compact engine mounted in a various working machine such as a carrying harvester, a chain saw, a lawnmower, a piggyback type harvester, a power spraying machine, an engine blower, a duster and a hedge trimmer, an engine starting device driven by a battery pack, and a manual working machine having the engine starting device.
2. Description of the Related Art
Currently, an engine starting device which starts a compact air-cooling type gasoline engine mounted in a manual working machine such as a widely used harvester and chain saw mostly includes a recoil type driving portion, a follower portion connected to a crankshaft of the engine through connecting/disconnecting means such as a centrifugal clutch, and a shock absorption•power accumulating portion which is disposed between the driving portion and the follower portion and which shock-absorbing driving force of the driving portion and which includes a spiral spring for resiliently accumulate force between the follower portion and the shock absorption•power accumulating portion. The recoil type driving portion includes a recoil reel around which a recoil rope is wound, and a recoil spiral spring which is disposed between the recoil reel and the casing. Inner and outer ends of the recoil spiral spring are respectively fixed to the recoil reel and the casing. The recoil reel is rotated in one direction by manually pulling out the recoil rope and at the same time, the recoil spiral spring is wound up to accumulate a spring force and in this state, if an operator moves his or her hand off the recoil rope, the accumulated force of the recoil spiral spring is released, and the recoil rope is automatically wound back around the recoil reel.
The recoil type driving portion requires a pulling operation for pulling out the recoil rope whenever the engine is started. In this pulling operation of the recoil rope, it is usually necessary to pull the recoil rope quickly and largely. Thus, if an operator has a weak strength or is an old person, or if the working space is small, the engine cannot be started with one pulling operation in many cases. Hence, many proposals have been made to facilitate the start of an engine by pulling the recoil rope, and some of them become commercially practical, but complicated properties of the pulling operation itself still remain. Significant progress has been made in recent compact electric motor or battery, and although they are extremely reduced in size, they have large capacities. In recent years, attention has been paid for an electric engine starting device capable of easily starting the engine at the flick of a switch to avoid the troublesome operability of the recoil type starting device, and it is desired to develop such engine starting device.
Such an electric compact engine starting device is disclosed in Japanese Utility Model Laid-Open Publication No. 63-110672. The starting device includes a DC motor to which electricity is supplied from a battery and which is driven by the battery, a spiral spring having a spiral spring barrel which is driven and wound by a worm gear fixed to an output shaft of the motor, an output rotation shaft to which an inner end of the spiral spring is fixed, a rotation shaft of an engine connected to the output rotation shaft through a one-way clutch, a turn-lever which stops the rotation of the output rotation shaft or releases the stop, a ganged electric switch which is operated such that it enters only when the rotation stop of the output rotation shaft is released by the lever, and an armature current control circuit which is driven by a motor at the tire of switching operation of the electric switch. The armature current control circuit keeps rotation of the motor even when the rotation shaft of the motor exceeds a set rotation speed to wind the spiral spring, and when the winding up operation of the spiral spring is completed, if the rotation speed becomes lower than the set rotation speed, electricity supply is cut and the armature current control circuit stops the rotation of the motor.
Japanese Patent Laid-Open Publication No. 2002-285940 discloses a starter apparatus. According to the starter apparatus, shock absorption•force accumulating means is interposed in an intermediate portion of a power transmitting system between a driving portion and a follower portion. The driving portion is an electric motor as a driving source. A worm connected and fixed to an output rotation shaft of the electric motor and a worm wheel provided on an outer periphery of the spiral spring barrel constitute a speed reducing mechanism. This configuration is substantially the same as that of the Japanese Utility Model Laid-Open Publication No. 63-110672. A recoil type driving portion is added to the driving side in addition to the electric motor. The recoil type driving portion includes a rope reel around which a recoil rope is wound and which is rotated when the recoil rope is pulled, a recoil spiral spring which reversely rotates the rope reel to wind up the recoil rope, and a recoil ratchet mechanism for transmitting the rotation of the rope reel to the shock absorption•force accumulating means. The spiral spring barrel can rotate only in one direction by a one-way clutch. From this configuration, it can be said that the starter of the Japanese Patent Laid-Open Publication No. 2002-285940 is merely a combination of the Japanese Utility Model Laid-Open Publication No. 63-110672 and a known recoil mechanism.
Japanese Patent Publication No. 2573340 discloses a spiral spring type starting device having a single frame. Accommodated in the frame are a battery, a DC electric motor driven by electricity of the battery, a control apparatus for controlling the operation and the stop of the motor, a highly speed reduction ratio speed reducing mechanism for transmitting power of the motor, a spiral spring force accumulating apparatus which is driven by the highly speed reduction ratio speed reducing mechanism, and a power transmitting apparatus only for transmitting a force of the force accumulating apparatus to the crankshaft. The highly speed reduction ratio speed reducing mechanism includes a first planet gear type speed reducer which is driven by a DC electric motor disposed on the other axis which is in parallel to the crankshaft, and a second speed reducer in which a driving gear provided on an output shaft of the planet gear type speed reducer is meshed with a follower gear which is integrally formed on an outer periphery of the spring force accumulating chamber of the force accumulating apparatus.
According to Japanese Utility Model Laid-Open Publication No. 2-13171, a spiral spring barrel is pivotally supported through a support system of a planet gear speed reducer disposed on the opposite side of a crankshaft of an engine such that the spiral spring barrel can rotate in one direction. The spiral spring barrel is decelerated and rotated by the planet gear speed reducer connected through a speed reducing spur gear pair including a small gear and a large gear fixed to an output shaft of a DC electric motor disposed in a housing. The one-way rotation at that time is carried out by engagement between the ratchet pawl and teeth provided on the outer periphery of the spiral spring barrel. An actuating ratchet wheel and an actuating ratchet pawl are disposed on the spiral spring barrel on the side of the crankshaft. When the engagement is released, the ratchet wheel can rotate. A starter ratchet wheel is assembled to the actuating ratchet wheel. The starter ratchet wheel engages with a centrifugal clutch pawl provided on the crankshaft.
The spiral spring barrel is integrally formed at its outer periphery with a ratchet wheel. A ratchet wheel having a small diameter meshes with an upper end of the spiral spring barrel. The rotation shaft fixed to the ratchet wheel having the small diameter can be rotated from outside using a manual crank. The manual crank is not inserted during a normal operation of the engine, and the ratchet wheel having the small diameter idles. If the starting operation ends in failure and attempt is made to insert the spiral spring again, the manual crank is inserted into the rotation shaft of the ratchet wheel having the small diameter, the spiral spring barrel is rotated, and force is accumulated in the spiral spring. When the engine is to be started, the actuating ratchet is operated to release the energy accumulated in the spiral spring, thereby rotating the starter ratchet wheel to crank and start the engine.
The battery used as a power supply of a starting device of an engine disclosed in Japanese Utility Model Laid-Open Publication No. 63-110672, Japanese Patent Laid-Open Publication No. 2002-285940, Japanese Patent Publication No. 2573340 and Japanese Utility Model Laid-Open Publication No. 2-13171 is a battery so-called NiCad battery or nickel metal hydride battery, and an accommodation space of the battery is not specified as described above. However, such battery is disposed in the starting device in many cases as described in Japanese Patent Publication No. 2573340 and Japanese Utility Model Laid-Open Publication No. 2-13171, and if not, the entire capacity of the conventional battery is increased and thus, the battery is disposed in its special space in the vicinity of the starting device in many cases. Further, if electricity required for an electric motor, which winds up the spiral spring of the force accumulating apparatus disposed between the engine and the engine starting electric motor is to be obtained from a battery, many batteries called NiCad batteries or nickel metal hydride batteries are naturally required. Thus, there is a limit for reducing the starting device in size and weight.
According to the engine starting device of the Japanese Utility Model Laid-Open Publication No. 63-110672, the spiral spring barrel is rotated in one direction by the meshing state between the worm gear which is directly coupled to the electric motor and the worm wheel formed on the outer periphery of the spiral spring barrel. Therefore, the spiral spring barrel does not reversely rotate, but in a power transmitting mechanism using the meshing state between the worm gear and the worm wheel, the direction of the output shaft of the electric motor and the rotation driving shaft of the spiral spring barrel intersect with each other at right angles, the efficiency is poor (about 60%) and the device cannot be reduced in size in terms of design. According to the engine starting device of the Japanese Utility Model Laid-Open Publication No. 63-110672, when the battery goes dead or the electric motor is broken, the engine starting device itself cannot be operated.
According to the Japanese Patent Laid-Open Publication No. 2002-285940, the spiral spring barrel is manually driven at the time of emergency by the recoil type drive mechanism, the entire apparatus corresponds to an apparatus in which the speed reducing mechanism is added to the conventional recoil type engine starting device as the electric motor, and since the speed reducing mechanism includes the worm and the worm wheel of the spiral spring barrel, the shaft of the electric motor and the support shaft of the spiral spring barrel is needed to intersect with each other at right angles, and it is difficult to reduce the entire apparatus in size.
According to the Japanese Patent Publication No. 2573340, the highly speed reduction ratio speed reducing mechanism is disposed between the electric motor and the spiral spring barrel, the motor capacity and the battery capacity are reduced in size to 1/10 and ⅙ as compared with the self starter type battery, this is practical even if a storage battery is provided, but the speed reduction ratio is set extremely large as large as 1/250 to 1/300. Thus, it takes a long time until the spiral spring barrel is rotated to obtain a predetermined force in the spiral spring. Therefore, in this engine starting device, an automatic winding control apparatus for the spiral spring is disposed, force accumulating operation of the force accumulating spring is automatically carried out whenever the starting operation is carried out once by the control circuit of the control apparatus, the timer or the winding up operation of the spiral spring is detected, the electricity to the motor is stopped, thereby reducing the waiting time at the time of the restarting operation. Thus, the entire apparatus becomes complicated, and its cost is naturally increased.
According to the Japanese Utility Model Laid-Open Publication No. 2-13171, when the electric motor becomes in its inoperative state, the manual crank is operated to rotate the spiral spring barrel through the ratchet wheel having the small diameter, the spiral spring is wound again, force is accumulated in the spiral spring, the manual crank is removed and then, the actuating ratchet is operated, thereby releasing the energy accumulated in the spiral spring, the starter ratchet wheel is rotated and the engine is started. However, the ratchet wheel having the small diameter idles during the rotation of the engine. Further, since the shafts of the electric motor, the spiral spring barrel, the ratchet wheel having the small diameter and the ratchet pawl are disposed in parallel to each other, this prevents the compact design of the engine starting device.
The present applicant previously proposed an electric engine starting device in Japanese Patent Application No. 2004-232139 in which unnecessary members are eliminated, the engine starting device is ultimately reduced in size and weight under rational design, and an engine can be started manually at the time of emergency.
According to its basic configuration, the engine starting device includes a compact electric motor driven by a battery, a power accumulating portion in which power of the compact electric motor is transmitted in a power accumulating direction through a highly speed reducer mechanism, and a power transmitting portion for transmitting the accumulated force of the power accumulating portion to a crankshaft of the engine, the engine starting device further including a spring and a rotation support member which supports one end of the spring, a spiral spring or a coil spring can be used as the spring, when the spring is the spiral spring, the rotation support member includes the spiral spring barrel, and if the spring is the coil spring, a normal gear can be used.
The support member is formed with a first gear, a second gear is fixed to the output shaft of the highly speed reducer mechanism, the first and second gears mesh with each other, the engine starting device further includes rotation preventing means in which the power accumulating portion or the power transmitting portion is disposed, the power accumulating portion or the power transmitting portion is allowed to rotate in a accumulated force releasing direction in a normal state, but when the electric motor is in its inoperative state, the rotation in the accumulated force releasing direction is prevented, and the engine starting device further includes a rotation operating mechanism which is disposed on an axis of the output shaft of the highly speed reducer mechanism, which can be engaged with and disengaged from a shaft end of the output shaft, and which can rotate the output shaft manually. The highly speed reducer mechanism is a planet gear type speed reducing mechanism, the rotation axes of the power accumulating portion and the power transmitting portion are disposed on the same axis of the crankshaft, the rotation shafts of the compact electric motor and the highly speed reducer mechanism are disposed in parallel to the crankshaft, and spur gears are used as the first and second gears.
As described above, the mechanical problems of the compact engine starting devices discloses in Japanese Utility Model Laid-Open Publication No. 63-110672, Japanese Patent Laid-Open Publication No. 2002-285940, Japanese Patent Publication No. 2573340 and Japanese Utility Model Laid-Open Publication No. 2-13171 are solved by the Japanese Patent Application No. 2004-232139, but there still remains a problem concerning how the compact engine starting mechanism is smoothly, reliably and safely driven using the compact battery. That is, in order to reduce the entire working machine in size and weight, it is not only important to start the engine, but it is also important that the battery itself which drives an ignition circuit and a fuel supply control circuit of the engine has sufficient discharging capacity and the battery is reduced in size and weight.
In addition to the engine starting devices disclosed in the Japanese Utility Model Laid-Open Publication No. 63-110672, Japanese Patent Laid-Open Publication No. 2002-285940, Japanese Patent Publication No. 2573340 and Japanese Utility Model Laid-Open Publication No. 2-13171, as a power supply of a starting device of a working machine having this kind of compact engine, the NiCad battery or nickel metal hydride battery are widely used as described above. A standard compact battery has usually 1.2 V. In order to drive an engine starting compact electric motor, at least 7.2 V is required. Thus, the compact electric motor can be driven if six batteries are used theoretically. However, in order to start the engine ideally, several more batteries are required, but such batteries have too much volume to be accommodated in a switch box disposed at a steering wheel of the working machine, and naturally the batteries must be disposed in the starting device or other special location, and in order to reduce the batteries in size and weight, it exceeds a permissible range. Even if an alkaline battery or an oxirite battery (1.5 V) is used, internal impedance (internal resistance) is high, and at least six batteries are required for obtaining the output voltage.
Thus, it is an object of the present invention to provide a high performance compact and light and safe battery pack which can be applied to a compact engine starting device of a working machine and which has high output.